This invention relates to phosphate laser glasses, typically neodymium-doped.
The term "laser" refers to the amplification of light by the stimulated emission of radiation. In a laser, an active material, for example, a glass suitably doped with an active atomic species such as neodymium, is placed in a cavity resonator formed by two reflecting, or at least partially reflecting, mirrors.
It is known for some time that phosphate laser glasses have a low threshold value for the laser effect, and phosphate glass compositions have been commercially available as optical components for use in laser systems.
Prior art phosphate laser glasses contain a wide variety of components including, for example, Al.sub.2 O.sub.3, SiO.sub.2, alkali metal oxides (Na.sub.2 O, K.sub.2 O, Li.sub.2 O, especially), alkaline earth metal oxides, etc., in addition to the base component, P.sub.2 O.sub.5. Prior art glasses having laser properties desirable for high energy solid state laser systems are described in U.S. Pat. Nos. 4,075,120; 4,248,732; and 4,239,645.
Other phosphate laser glasses place emphasis on the use of K.sub.2 O and BaO to impart pronounced a thermal character to the laser glass. See, e.g., U.S. Pat. No. 4,022,707; U.S. Pat. No. 4,076,541; and U.S. Pat. No. 4,108,673. While other publications require the use of Li.sub.2 O, e.g., U.S. Pat. No. 4,929,387, and/or MgO, e.g., U.S. Pat. No. 5,032,315, to obtain glasses with exceptional properties for use in high average power laser systems. Still another publication, U.S. Pat. No. 4,333,848, emphasizes the use of Li.sub.2 O with BaO to achieve this athermal characteristic in a laser glass.
Still other laser glass publications exist which prescribe the necessary use of SiO.sub.2, e.g., U.S. Pat. No. 4,820,662, DE 34 35 133, JP 51-107312, and DE 36 09 247, and/or B.sub.2 O.sub.3, e.g., U.S. Pat. No. 4,661,284, to obtain improvements in the characteristics desirable in laser glasses for high power solid state laser systems.
Many other laser phosphate publications exist which describe a wide variety of glasses such as JP 49-114615(4), JP 60-191029(3), JP 51-107311, JP 50-3411, JP 51-30812, SU-355,916, U.S. Pat. No. 3,846,142. In these patents, no particular emphasis is placed on alkali metal oxides. Further patents equate all metal oxides, e.g., U.S. Pat. No. 4,120,814, U.S. Pat. No. 3,979,322, U.S. Pat. No. 4,225,459, U.S. Pat. No. 3,580,859, and U.S. Pat. No. 4,470,922.
JP 54-38311 indicates a preference for Li.sub.2 O, but in phosphate glasses containing components such as CuO and V.sub.2 O.sub.5.
Integrated optic lasers and amplifiers have been demonstrated in neodymium-doped glasses. These devices have operated near 1057 nm in silicate glasses and 1057 and 1355 nm in phosphate glasses (Sanford et al., Opt. Lett. 15, 366 (1990); Aoki et al., IEEE Photon. Tech. Lett. 2, 459 (1990); and Aoki et al., Elec. Lett. 26, 1910 (1990)).
The wavelength area around 1.3 .mu.m is of particular importance to the telecommunications industry since it is in this wavelength region where commercial transmission fibers are characterized by low optical loss and near zero optical dispersion. Thus, most of the optical fiber communications systems in use presently operate near 1.3 .mu.m, and active devices which function near 1.3 .mu. are consequently required to act as both laser sources and as optical amplifiers.
Laser action at 905 nm has been realized in neodymium-doped-silica fiber lasers but not in glass integrated optic devices (Poet al., Digest of Annual Meeting of the Optical Society of America, Optical Society of America, paper FD-4 (1986)) .